The Christian should be 100% correct in understanding the Godhead. Since the Nicene Council in 325 A.D. the foundational doctrine of the Catholic Church,the Holy Trinity ( absolutely unscriptural word) was based upon the many gods of Rome. 

The Romans had many gods to whom they prayed. They also prayed to ancestors as mediators. It was a way of giving new names to old gods, so we have saints to make it more Biblical.Thus instead of Jupiter, Venice, Mars etc, we have Paul, Peter, Fatima etc. They could not make their Pagan religion work out with just one God, so they split Him up into three, and made intercessors of the saints as they had made intercessors of their ancestors.Ever since then people have failed to realize that there is just one God with three offices or manifestations. 

This is what the Bible says. It doesn'nt say a thing about a first or second or third personhere.It says that God
 was manifest in the flesh. ONE GOD.That ought to settle it .God came in a human form. That did'nt make Him ANOTHER GOD. HE WAS GOD,THE SAME GOD. It was a revelation then, and it is a revelation now! ONE GOD!
 In the beginning was the Word, and the Word was with God, and the  Word was God. St.John 1v1. 
 He that hath seen me hath seen the father. St,John 14v9.
 For in him dwelleth all the fulness of the Godhead bodily. Colossians 2v9
 
I and my Father are one. John10v30.                                                                                                          .
One Lord, one faith, one baptism.Ephesians4v5.